The principal goal is to investigate the functional organization of neurons in visual cortex. This information is critical to understanding how neural circuits perform the computations subserving visual perception, and it holds the promise of informing efforts to remediate.disorders of vision. The proposed studies will focus on primary visual cortex (V1) of squirrel monkey and will address the fine-scale organization of cells using both intrinsic optical imaging and calcium imaging with two-photon laser-scanning microscopy. Large-scale functional maps of V1 will first be made with conventional optical imaging. Next, the two-photon technique will be used to examine the activity of neurons in identified regions with single-cell resolution. These will be the first measurements of their kind in primates. Briefly, the specific aims include: 1) investigating the finescale clustering of color-selective neurons in V1, and understanding how other response properties, including orientation, direction, and spatial frequency preferences, are distributed with respect to color selectivity; and 2) examining the micro-organization of orientation and direction selectivity in relation to gross orientation maps, both within iso-orientation domains and at discontinuities such as pinwheel centers.